In this paper a new method for the evaluation and comparison of potential future electricity systems is presented. The German electricity system in the year 2050 is used as an example. Based on a comprehensive scenario analysis defining a corridor for possible shares of fluctuating renewable energy sources (FRES) residual loads are calculated in a unified manner. The share of electricity from PV and wind power plants in Germany in the year 2050 is in a range of 42-122% and the load demand has a bandwidth of around 460-750 TWh. The residual loads are input for an algorithm that defines a supplementary mix of technologies providing flexibility to the system. The overall system layout guarantees the balance of generation and demand at all times. Due to the fact that the same method for residual load calculation and mixture of technologies is applied for all scenarios, a good comparability is guaranteed and we are able to identify key characteristics for future developments. The unique feature of the new algorithms presented here is the very fast calculation for a year-long simulation with hourly or shorter time steps taking into account the state of charge or availability of all storage and flexibility technologies. This allows an analysis of many different scenarios on a macro-economic level, variation of input parameters can easily be done, and extensive sensitivity analysis is possible. Furthermore different shares of FRES, CO2-emission targets, interest rates or social acceptance of certain technologies can be included. The capabilities of the method are demonstrated by an analysis of potential German power system layouts with a base scenario of 90% CO2-reduction target compared to 1990 and by the identification of different options for a power sector with a high degree of decarbonisation. The approach also aims at a very high level of transparency both regarding the algorithms and regarding the input parameters of the different technologies taken into account. Therefore this paper also gives a comprehensive and complete overview on the technology parameters used. The forecast on all technologies for the year 2050 regarding technical and economic parameters was made in a comprehensive consultation process with more than 100 experts representing academia and industry working on all different technologies. An extensive analysis of options for the design of potential German energy supply systems in 2050 based on the presented methodology will be published in a follow-up paper.

Relevant aspects of the options and requirements for reducing and phasing out coal-fired power generation have been under debate for several years. This process has produced a range of strategies, analyses and arguments, outlining how coal use in the energy sector could be reduced and phased out in the planned time frame, and determining structural policy measures suitable to support this. This Coal Report studies the existing analyses and provides an overview of the state of debate. It is intended to provide information on facts and contexts, present the advantages and disadvantages of individual courses of action, and reveal the respective scientific backgrounds. It strives to take a scientific and independent approach, and present facts in concise language, making it easy to follow for readers who are not experts in the field, without excessive abridgements or provocative statements.

Wind energy that can neither be fed into the grid nor be used regionally must be curtailed. This paper proposes different options to deal with such surplus wind energy amounts in a time horizon until 2020. It assesses their ability to handle the surplus energy in a sustainable way using a multi criteria analysis. The paper bases on a study that was prepared for the Ministry for Climate Protection, Environment, Agriculture, Nature Conservation and Consumer Protection of North Rhine-Westphalia between 2010 and 2012.